Arsenic acid can be readily prepared by dissolving arsenic pentoxide in water or by dissolving arsenic trioxide in the presence of an oxidizing agent The oxides of arsenic are often prepared from solutions obtained in the metallurgical treatment processes of arsenical materials such as ores, concentrates, fumes, speisses, slags, residues, flue dusts and the like Depending on the arsenical material being treated, these processes often include a leach with a lixiviant yielding a solution that contains arsenic in the form of an arsenite or arsenate. The leach may be carried out at atmospheric pressure, elevated pressures, at elevated temperatures and, in many cases, in the presence of an oxygen-containing gas. Concurrent with the leaching of arsenic, other metals are dissolved that contaminate the solution and, ultimately, also contaminate the arsenic product prepared from such a solution In many cases, the arsenic-containing solution is treated for the formation of arsenic compounds that may be disposed in an acceptable form.
The leaching of arsenical materials, the oxidation of trivalent to pentavalent arsenic and the preparation of arsenic compounds are well documented. The prior art, however, is silent on the process according to the present invention according to which arsenic acid is prepared from a soluble arsenate salt solution by electrolysis with membranes.